The present invention relates to a pivoting door thrust reverser for a turbojet engine, more particularly a thrust reverser having a passage in the pivoting thrust reverser door to deflect gases in a reverse thrust direction.
Turbofan-type turbojet engines are well known in the art and typically comprise a fan at the front of the turbojet engine which directs a flow of bypass air through a duct bounded by the engine cowling on the inside and a fan cowling on the outside. The generally annular duct bounded by the engine cowling and the fan cowling may channel both the bypass flow and the primary exhaust gas flow at a downstream portion or may channel only the bypass flow.
In aircraft on which the turbojet engine is mounted outside of the airframe structure, the fan cowling and the engine cowling are configured to form boundaries of the bypass flow duct and to provide aerodynamic outer surfaces to reduce drag.
FIG. 1 illustrates a known pivoting door-type thrust reverser associated with the fan cowling of a turbofan-type turbojet engine. As illustrated, the forward portion of the fan cowling 1 defines the outer limits of the bypass flow duct and is generally concentrically arranged about the turbojet engine (not shown). The cowling 1 comprises an external cowling panel 4 and an internal cowling panel interconnected by a frame 6. The outer surface of the external cowling panel has an aerodynamic surface over which the air external to the engine passes during aircraft flight. The inner surface of the inner cowling panel defines the outer boundary of the bypass flow duct through which the bypass air flow passes in the direction of the arrow.
The fan cowling also comprises a thrust reverser, illustrated generally at 2, and a rear fairing 3. The thrust reverser 2 comprises a door 7 pivotally attached to the cowling such that it is movable between a closed, forward thrust position, illustrated in FIG. 1, and an open, reverse thrust position in which the upstream end (towards the left as viewed in FIG. 1) of the thrust reverser door 7 is moved outwardly from the cowling, while a downstream portion is moved inwardly into the bypass flow duct airstream so as to redirect at least a portion of the bypass flow through an opening in the fan cowling in a direction that has a reverse thrust component.
An actuator 8 for moving the door 7 between its forward and reverse thrust positions may comprise a hydraulic cylinder mounted to the frame 6, and having an extendible and retractable piston rod connected to the thrust reverser door 7.
The thrust reverser door 7 has an outer door panel 9 and an inner door panel 11 joined together by an internal structure. The upstream end of the door 7 may have a deflector 13 to maximize the efficiency of the thrust reverser when the door 7 is in the reverse thrust position. When the door is in the forward thrust position, as illustrated in FIG. 1, the outer door panel 9 is substantially flush with the external surfaces of the upstream panel and the downstream fairing 3.
A plurality of thrust reverser doors 7 may be incorporated into the fan cowling, such doors being circumferentially spaced around the periphery of the fan cowling. A portion of the fan cowling axially extends between forward and rear portions of the cowling between circumferentially adjacent thrust reverser doors 7 to provide structural rigidity to the fan cowling and to provide pivot mounting points for attaching the doors 7 to the fan cowling. French Patents 1,482,538 and 2,030,034 illustrate typical, known thrust reversers.
U.S. Pat. No. 3,605,411 discloses a pivoting door-type thrust reverser in which the deflector mounted on the upstream or forward end of the thrust reverser door is movable to an extended position when the door is in the reverse thrust position.
French Patent 2,618,853 discloses a thrust reverser in which the deflector is retracted when the door is in its forward thrust position to optimize engine performance.
In some applications, as illustrated in FIG. 1, the deflector 13 projects from the inner panel 11 of the thrust reverser door 7 even when the door is in its forward thrust position without extending into the bypass flow duct. This forms a cavity 16 facing inwardly into the bypass flow duct which will slightly degrade engine performance.
French Patent 2,680,547 discloses a thrust reverser having a combination of spoilers and deflectors to attempt to optimize the direction of exhaust flow.
The above-described known thrust reversers incur major drawbacks because of the aerodynamic size constraints on the flow passages cleared by the thrust reverser doors which cause the doors to be biased in the open, thrust reversing direction. The full cross-section of the flow passages must be larger than the associated duct cross-section in a plane taken upstream, or forward, of the door on account of the pressure losses due to the gas flow deflection since the downstream, or rearward portion of the duct unobstructed by the inwardly protruding portion of the thrust reverser doors is minimized in order to produce an appropriate reverse thrust force.
Quite obviously, the bias of the doors toward the open or reverse thrust position is a safety drawback. The reverser would be safer if the thrust reverser door was biased towards the closed or forward thrust position. This consideration also applies to a thrust reverser door that would tend to close again under pressure even if they were partially deployed towards the thrust reversing position.
In some cases, the effect of the pressure acting on the thrust reverser door is such that very high stresses are transmitted through the thrust reverser door actuators between their attachment points to the upstream portion of the cowling and the doors. As a consequence, this structure and the door locking mechanisms must be undesirably heavy.
U.S. Pat. No. 3,612,401 discloses an outer flow panel hinged at its rear edge in which the forward edge pivots into the gas flow duct. In this configuration, the outer and inner panels operate separately from each other to direct the flow towards the front of the cowling.
French Patent Application to 2 121 563 discloses a jet engine thrust reverser having a pivoting door in which the rear edge of the pivoting door extends into the annular gas flow duct while the forward edge portion extends outwardly from the cowling.